Solving power problems

Use this information to solve power problems.

Power problems can be difficult to solve. For example, a short circuit can exist anywhere on any of the power distribution buses. Usually, a short circuit will cause the power subsystem to shut down because of an overcurrent condition. To diagnose a power problem, use the following general procedure:

  1. Turn off the server and disconnect all power cords.
  2. Check for loose cables in the power subsystem. Also check for short circuits, for example, if a loose screw is causing a short circuit on a circuit board.
  3. Check the lit LEDs on the operator information panel (see Light path diagnostics).
  4. If the check log LED on the light path diagnostics panel is lit, check the IMM event log for faulty Pwr rail and complete the following steps. Table 1 identifies the components that are associated with each Pwr rail and the order in which to troubleshoot the components.
    1. Disconnect the cables and power cords to all internal and external devices (see Internal cable routing and connectors). Leave the power-supply cords connected.
    2. For Pwr rail A error, complete the following steps:
      1. (Trained technician only) Replace the system board.
      2. (Trained technician only) Replace the microprocessor.
    3. For other rail errors (Pwr rail A error, see step 4.b), remove each component that is associated with the faulty Pwr rail, one at a time, in the sequence indicated in Table 1, restarting the server each time, until the cause of the overcurrent condition is identified.
      Table 1. Components associated with power rail errors.

      The power rail error table with one level of row and column headers.
      Pwr rail error in the IMM event log Components
      Pwr rail A error
      • Microprocessor 1
      Pwr rail B error
      • Microprocessor 2
      Pwr rail C error
      • Adapter (if one is installed) in PCI riser-card assembly 1
      • PCI riser-card assembly 1
      • Fan 1
      • DIMMs 1 through 6
      Pwr rail D error
      • Dual-port network adapter
      • Fan 2
      • DIMMs 7 through 12
      Pwr rail E error
      • Hard disk drives
      • DIMMs 13 through 18
      Pwr rail F error
      • Adapter (if one is installed) in PCI riser-card assembly 1
      • PCI riser-card assembly 1
      • Fan 4
      • DIMMs 19 through 24
      Pwr rail G error
      • PCI adaptor power cable (if one is present)
      • Fan 3
      • Hard disk drives
      • Hard disk drive backplane assembly
      Pwr rail H error
      • Hard disk drive power cable
      • Hard disk drives
      • Hard disk drive backplane
      or
      • PCI adapter power cable
      • Adapter installed in PCI riser-card assembly 2
      • PCI riser-card assembly 2
    4. Replace the identified component.
  5. Remove the adapters and disconnect the cables and power cords to all internal and external devices until the server is at the minimum configuration that is required for the server to start (see Power-supply LEDs for the minimum configuration).
  6. Reconnect all power cords and turn on the server. If the server starts successfully, reseat the adapters and devices one at a time until the problem is isolated.

If the server does not start from the minimum configuration, see Power-supply LEDs to replace the components in the minimum configuration one at a time until the problem is isolated.

Parent topic: Troubleshooting